108 PALEONTOLOGY OF NEW YORK. 



only one ut' the genus yet I'uuud in the Schohurie grit. It diflers Iruni 

 A. mvricata in its narrower and more oblique body and shorter wing, as 

 measured along the post-cardinal slope. 



Formation and locality. In the Schoharie grit, at Schoharie, N. Y. 



ACTINOPTERIA MURICATA. 



PLATE XVII, FIGS. 1-3. 



Av'irida iniir'uata, II.ti.L. Geol. Siu-v. N. Y. : Ri'j). Fourth Di.st., ji. ISl. 1S43. 



Ptenmites murivatun, H.ii.l. Cut. Am. Pal. Foss. : S. A. Miller, i>. 202. 1877. 



Actijiopteria muricala, }l\i.\.. Pal. N. Y., vol. v, pt 1. Plates and Explanations : PI. 17, lif.'-s. 1-3. Jan., 1S83. 



SiiELi- small, sub-rhomboidal : body sub-ovate, very oblique ; length one-third 

 greater than the height; margin rounded below, turning abruptly backward 

 on the posterior side, and extending in a direct line to the beak. 



Left valve convex, llight valve unknown. 



Hinge-line straight I'rom the beak to the po.sterior extremity, .-^loping 

 downward on the anterior side; entire length greater than that of the body 

 ol" the shell. 



lieak acute, arching over the hinge, inclined I'orward, situated at the 

 anterior third of the hinge-line. Umbonal region subtending an acute angle. 



Ear broad-triangular, separated from the body of the shell by a broad 

 undefined sulcus which is limited by a strong sub-angular fold extending 

 from the beak, and by the deep rounded byssal sinus ; margin convex ; 

 extremity obtuse. AVing flat, triangular, defined by having more subdued 

 surface rays; margin deeply sinuate; extremity mucronate. 



Test thin, marked with from eight to twelve strong, filiform rays, with 

 finer intermediate ones in the broad, flat interspaces. The rays on the wing 

 are somewhat subdued. Surface crossed l)y fine concentric lines of growth, 

 which, at intervals, are crowded and raised into lamellae, and on the rays are 

 produced into tubular spines. These spines are seen only in the better pre- 

 served specimens, and appear in the casts as elongate elevations upon the 

 rays. The concentric strise are conspicuous in the anterior sulcus. 



Interior unknown. 



